Author: Jon Dart
Date: 11:08:26 09/20/99
Go up one level in this thread
Arasan doesn't generate rook or bishop underpromotions except at ply 0 (I think Crafty does the same thing). Forward pruning is a reasonable thing to do. In the qsearch, I do something like: if (current material + gain from promotion + some constant < alpha) skip move My latest build has this output on your example: ply 4. Kh3 0 seconds. score: -7.19 215 nodes. ply 5. Kh3 0 seconds. score: -7.19 283 nodes. ply 5. Kh3 0 seconds. score: -11.08 470 nodes. ply 6. Kh3 0 seconds. score: -11.08 1144 nodes. ply 7. Kh3 0 seconds. score: -11.11 2538 nodes. ply 8. Kh3 0 seconds. score: -11.28 4856 nodes. ply 9. Kh3 0 seconds. score: -11.28 5172 nodes. ply 9. Kh3 0 seconds. score: -17.02 9453 nodes. ply 10. Kh3 0 seconds. score: -17.52 19403 nodes. ply 11. Kh3 0 seconds. score: -17.52 20700 nodes. ply 11. Kh3 0 seconds. score: -156.00 50050 nodes. --Jon On September 20, 1999 at 02:09:30, Steffen Jakob wrote: >Hi all! > >I still try to improve the playing skill of Hossa in pawn endgames (which is not >very difficult because he plays them very badly). About underpromotions: I know >that Amir Ban doesn't generate underpromotions in the search tree. I don't like >that very much. What I am doing now is to reduce the search depth for >underpromotions (one ply). It helps a lot in some positions, e.g. in the pawn >endgame position where crafty saw that mate in 4 although it is a mate in 6. As >you can see below I need 158616 nodes to see the mate without pruning and 135713 >with underpromotion pruning. I think about reducing the depth by two plies for >bishop underpromotions (can someone please give me some positions where the >winner move is to promote the pawn to a bishop?). What are you thinking about >this? Are there other ways to prune underpromotions? E.g. if you are sure that >queen promotions are searched before underpromotions and alpha > xxx then it >might be useless to try those moves (at least rook and bishop promotions). > >analysis without forward pruning: >--------------------------------- > > +---+---+---+---+---+---+---+---+ >8 | | | | | | | | | > +---+---+---+---+---+---+---+---+ Black: Hossa v1.63 (C) (0) >7 ||P|| | | | | | | | > +---+---+---+---+---+---+---+---+ Black material: 4 >6 | P | | | | | ||P|| | > +---+---+---+---+---+---+---+---+ >5 | | | | | | | ||P|| > +---+---+---+---+---+---+---+---+ White to move >4 | | | | | | | | P | > +---+---+---+---+---+---+---+---+ 8/p7/P5p1/7p/7P/4kpK1/8/8 w >3 | | | | ||K|||P|| K | | > +---+---+---+---+---+---+---+---+ White material: 2 >2 | | | | | | | | | > +---+---+---+---+---+---+---+---+ White: opponent (0) >1 | | | | | | | | | > +---+---+---+---+---+---+---+---+ > a b c d e f g h > > > depth value time nodes pv > 1 -5.23 0.00 2 1.g3h3 > <1> -5.23 0.00 3 1.g3h3 > 2 -5.35 0.00 38 1.g3h3 f2 2.h3g2 > <2> -5.35 0.00 48 1.g3h3 f2 2.h3g2 > 3 -5.37 0.00 84 1.g3h3 f2 2.h3g2 e3e2 > <3> -5.37 0.00 90 1.g3h3 f2 2.h3g2 e3e2 >? 4 -510.92 0.01 194 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q >? <4> -510.92 0.01 207 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 5 -510.92 0.01 322 1.g3h3 f2 2.h3g2 > <5> -510.92 0.01 335 1.g3h3 f2 2.h3g2 > 6 -510.92 0.01 531 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > <6> -510.92 0.01 552 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 7 -510.92 0.02 1182 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 f2f1Q > 4.h2g3 > <7> -510.92 0.02 1203 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 f2f1Q > 4.h2g3 > 8 -510.98 0.05 2817 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 e2f3 > 4.h2h3 f2f1Q 5.h3h2 > <8> -510.98 0.05 2867 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 e2f3 > 4.h2h3 f2f1Q 5.h3h2 > 9 -510.97 0.09 5587 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 f1f2 5.h2h3 e2f3 > <9> -510.97 0.09 5644 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 f1f2 5.h2h3 e2f3 >? 10 -512.01 0.24 14405 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 e2e3 5.h2g3 f1xa6 >? <10> -512.01 0.24 14556 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 e2e3 5.h2g3 f1xa6 > 11 -512.03 0.64 41493 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 e2e3 5.h2g3 f1xa6 6.g3g2 > <11> -512.03 0.65 41840 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 e2e3 5.h2g3 f1xa6 6.g3g2 >? 12 #-6 2.11 158616 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 g5 5.h4xg5 e2f3 6.g6 f1g2 >? <12> #-6 2.12 159367 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 g5 5.h4xg5 e2f3 6.g6 f1g2 > > >analysis with forward pruning: >------------------------------ > > depth value time nodes pv > 1 -5.23 0.00 2 1.g3h3 > <1> -5.23 0.00 3 1.g3h3 > 2 -5.35 0.00 38 1.g3h3 f2 2.h3g2 > <2> -5.35 0.00 48 1.g3h3 f2 2.h3g2 > 3 -5.37 0.00 84 1.g3h3 f2 2.h3g2 e3e2 > <3> -5.37 0.00 90 1.g3h3 f2 2.h3g2 e3e2 >? 4 -510.92 0.01 194 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q >? <4> -510.92 0.01 207 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 5 -510.92 0.02 322 1.g3h3 f2 2.h3g2 > <5> -510.92 0.02 335 1.g3h3 f2 2.h3g2 > 6 -510.92 0.03 531 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > <6> -510.92 0.03 552 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 7 -510.92 0.03 1182 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 f2f1Q > 4.h2g3 > <7> -510.92 0.03 1203 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 f2f1Q > 4.h2g3 > 8 -510.98 0.04 2726 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 e2f3 > 4.h2h3 f2f1Q 5.h3h2 > <8> -510.98 0.04 2776 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 e2f3 > 4.h2h3 f2f1Q 5.h3h2 > 9 -510.97 0.08 5403 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 f1f2 5.h2h3 e2f3 > <9> -510.97 0.08 5460 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 f1f2 5.h2h3 e2f3 >? 10 -512.01 0.16 12077 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 e2e3 5.h2g3 f1xa6 >? <10> -512.01 0.16 12228 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 e2e3 5.h2g3 f1xa6 > 11 -512.03 0.46 33004 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 e2e3 5.h2g3 f1xa6 6.g3g2 > <11> -512.03 0.46 33351 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 e2e3 5.h2g3 f1xa6 6.g3g2 >? 12 #-6 1.71 135713 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 g5 5.h4xg5 e2f3 6.g6 f1g2 >? <12> #-6 1.72 136462 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q > 4.g3h2 g5 5.h4xg5 e2f3 6.g6 f1g2 > > >Best wishes, >Steffen.
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